Set fso=Wscript.CreateObject("Scripting.FileSystemObject")
flrName="D:\Workspace\src\" 'dir that you need deal with
count=0 'get the count of modified files
function Traversal(dir)
set flr=fso.getfolder(dir)
set fs=flr.files
findstr1="[assembly: SecurityTransparent]" 'find string that need to be replaced
findstr2=replace(findstr1," ","") 'becasuse there is space char in findstr,so add this findstr2
replaceStr="[assembly: AllowPartiallyTrustedCallers()]" 'destination string in replace

for each f in fs
if lcase(f.name)="assemblyinfo.cs" then
set findf=fso.opentextfile(f)
do while findf.atendofstream=false
d=f.datelastmodified 'get modified datetime of current file
alltext=findf.readall

if(InStr(alltext,findstr1) > 0 ) then
s=replace(alltext,findstr1, replaceStr)
count=count+1
findf.close()
'If no findstr2, delete the following elseif block
elseif(InStr(alltext,findstr2) > 0) then
s=replace(alltext,findstr2, replaceStr)
count=count+1
findf.close()

else
findf.close()
exit do
end if

set r=fso.opentextfile(f, 2, true)
r.write s

d2=f.datelastmodified

if d2>=d then exit do
loop

end if
next

set fs=flr.subfolders
for each f in fs
Traversal(f.path)
next

end function

Traversal(flrName)
'msgbox ("Done! " count " files were modified successfully.")
wscript.echo "Done! " count " files were modified successfully." 'value popup by "wscript.echo" can be received by .bat easily

Wscript.quit count 'this variable "count" in order to get a return value by %ErrorLevel%

@echo off
for /f "delims=" %%a in ('cscript //nologo c:\t.vbs') do (
set ScriptOut=%%a)
echo Result: %ScriptOut%

@echo off
cscript //nologo c:\t.vbs
echo -----Modify %ErrorLevel% "AssemblyInfo.cs" files successfully.-----